Valve annulus constriction apparatus and method

ABSTRACT

An apparatus is described for supporting and/or constricting a surface of a valve annulus. The apparatus includes a tubular member of dimensions suitable for insertion into a body vessel. The tubular member includes at least two first segments attachable to an interior wall of the body vessel. The tubular member further includes at least one second segment which is capable of decreasing its axial length to draw one of the first segments towards the other first segment.

BACKGROUND

[0001] 1. Field

[0002] Stent like structures for insertion into body vessels, and thetreatment of valve insufficiency.

[0003] 2. Background

[0004] Generally speaking, oxygenated blood travels from the lungs tothe left atrium by way of the pulmonary veins. The veins from thesystemic circuit, the venae cavae and coronary sinus carry blooddeficient in oxygen into the right atrium. The right ventricle takesblood received from the right atrium and sends it to the lungs, whilethe left ventricle takes blood received from the left atrium and sendsit to the aorta.

[0005] The atrioventricular valves between respective ones of the atriaand ventricles play important roles in the transport of blood throughthe body. The atrioventricular valves open during diastole, when theheart muscle relaxes, to allow blood to flow from the atria into theventricles. The atrioventricular valves close during systole, when theheart muscle contracts, preventing the back flow of blood into the atriaand allowing blood from the ventricles to be efficiently pumped into thelungs via the pulmonary tract and to the rest of the body via the aorta.

[0006] The mitral valve is the atrioventricular valve that controlsblood flow from the left atrium into the left ventricle. The mitralvalve is a bicuspid valve, describing the two cusps or leaflets thatopen and close the valve. The cusps or leaflets are attached to amuscular and fibrous ring around the orifice (mitral valve annulus) andtheir apices hang down into the left ventricle. When the ventricle fillswith blood and begins to contract, the valve cusps or leaflets flow intoposition in the atrioventricular opening and are forced shut (coaptate)by the increasing pressure. To prevent the valve cusps or leaflets fromturning into the left atrium and regurgitating blood, tendinous cords,the chordae tendineae, are attached to the free margins and ventricularsurfaces of the cusps or leaflets. At the other ends, these cordsattached to one of a respective pair of papillary muscles projectingfrom the ventricular wall. By contracting, these muscles maintain theintegrity of the valve during ventricular contraction or systole.

[0007] When the two cusps or leaflets of the mitral valve do notcompletely close, there is backflow, or regurgitation of blood. Thebackflow increases the pressure in the left atrium which leads topulmonary hypertension and dilation of the heart which are commonsymptoms of congestive heart failure. A heart then has to work harderpumping blood for the body which can lead to heart damage. Incompleteclosing of the mitral valve cusps or leaflets is common, occurringgenerally in about seven percent of the population. Conditionscontributing to incomplete closure of the mitral valve cusps or leafletsinclude genetic defects, infections, coronary artery disease, myocardialinfarction, or congestive heart failure. These conditions contribute tomitral valve regurgitation resulting from enlargement of the mitralvalve annulus and/or movement of the papillary muscles away from thevalve as a result of ventricular enlargement. When the annulus enlarges,the cusps or leaflets of the valve are no longer able to close(coaptate), because the distance between the two cusps or leaflets hasincreased too much for the cusps or leaflets to touch each other andthus close off blood flow to the left atrium during, for example,systole. Mitral valve regurgitation can also result as a secondaryetiology due to the remodeling of a distorted left ventricle in ischemicheart disease. It is known that as the ventricle is remodeled, thepapillary muscles can be displaced away from their natural position.This displacement alters the natural tethering of the cusps or leafletsand restricts the ability of the cusps or leaflets to close properly atthe level of the annulus.

[0008] In general, most cases of mitral valve regurgitation are mild andthe symptoms may be controlled with drugs. In more serious cases, themitral valve can be repaired through a procedure known as annuloplasty,a surgical procedure in which a synthetic ring is placed around thevalve annulus. Annuloplasty encourages aptation of the mitral valvecusps or leaflets by shrinking the size of the valve opening. In otherinstances, a faulty mitral valve must be surgically replaced with a newvalve. These surgical repairs require the opening of the chest bysternotomy or at best through small incisions in the chest wall, heartlung bypass and stopping the heart beat. In general, annuloplasty is anextremely invasive procedure, and, as such, a less invasive treatmentfor annular dilation is desirable.

SUMMARY

[0009] In one embodiment, an apparatus is provided for supporting and/orconstricting a surface of a valve annulus. The apparatus includes atubular member of dimensions suitable for insertion into a body vessel.The tubular member includes at least two first segments attachable to aninterior wall of the body vessel. The tubular member further includes atleast one second segment which is capable of decreasing its axial lengthto draw one of the first segments towards the other first segment.

[0010] In one embodiment, the tubular member may be used to stabilize ormodify a length of a blood vessel. Representatively, when placed, forexample, in coronary arteries and/or veins, the tubular member may beused to constrict a surface of an atrioventricular valve annulus, suchas the mitral valve annulus that is in close proximity to the coronaryarteries and/or veins. The apparatus may also be used to constrict thetricuspid valve annulus. The apparatus and method are useful fortreating mitral valve dilation and regurgitation, among other problems.The apparatus may also be used to support and/or constrict other valvesor structures in a human or animal body.

[0011] In a further embodiment, a method is described. The methodincludes inserting a tubular member into a body vessel and securingattachable portions of the tubular member to an interior wall of thebody vessel. In one implementation, the tubular member secured to thebody vessel serves to prevent a portion of the body vessel fromincreasing in length. In another implementation, the tubular membersecured to the body vessel serves to constrict a portion of the bodyvessel by causing a length of the tubular member between the attachableportions to be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The features, aspects, and advantages of the disclosed subjectmatter will become more fully apparent from the following detaileddescription and appended claims when taken in conjunction withaccompanying illustrations in which:

[0013]FIG. 1 is an illustration of an embodiment of a segmented stent;

[0014]FIG. 2 is a close up illustration of an embodiment of unexpandedshrink segment;

[0015]FIG. 3 is a close up illustration of expanded shrink segment;

[0016]FIG. 4 is an illustration of an embodiment of a segmented balloon;

[0017]FIG. 5 is an illustration of an embodiment of a segmented balloonhaving segments inflated to correspond with a first group of segments ofa stent;

[0018]FIG. 5A is an illustration of a cross-sectional view of thesegmented balloon taken along line A-A′ of FIG. 5.

[0019]FIG. 5B is an illustration of a cross-sectional view of thesegmented balloon taken along line B-B′ of FIG. 5.

[0020]FIG. 6 is an illustration of an embodiment of a segmented stenthaving a first group of segments expanded and a second group ofunexpanded segments;

[0021]FIG. 7 is an illustration of an embodiment of a segmented balloonhaving segments inflated to correspond with a first group and a secondgroup of segments of a stent;

[0022]FIG. 8 is an illustration of an embodiment of a segmented stenthaving segments of a first group and segments of a second groupexpanded;

[0023]FIG. 9 is an illustration of an embodiment of a segmented stenthaving a group of segments with struts angled at a 30-degree angle;

[0024]FIG. 10 is an illustration of an embodiment of a segmented stenthaving a first group of segments with struts angled at a 30 degreeangle, wherein the segments are expanded;

[0025] FIGS. 11-14 are illustrations of various embodiments of a radialtraction segment;

[0026]FIG. 15 is an illustration of an embodiment of a segmented balloonhaving a first group of segments inflated, and one segment from a secondgroup inflated;

[0027]FIG. 16 is an illustration of an embodiment of a segmented stenthaving a first group of segments expanded, and one segment from a secondgroup expanded;

[0028]FIG. 17 is an illustration of an embodiment of a segmented balloonhaving a first group of segments inflated, and one segment from a secondgroup partially inflated;

[0029]FIG. 18 is an illustration of an embodiment of a segmented stenthaving a first group of segments expanded, and one segment from a secondgroup partially expanded;

[0030]FIG. 19 is an illustration of an embodiment of a segmented balloonhaving a first group of segments inflated, and one segment from a secondgroup fully inflated after being partially inflated;

[0031]FIGS. 20 and 21 are illustrations of balloon segments having arange of expandability;

[0032]FIG. 22 is an illustration of an embodiment of a segmented stenthaving a first group of segments expanded, and one segment from a secondgroup fully expanded after being partially expanded;

[0033]FIG. 23 is an illustration of an embodiment of a human heart;

[0034]FIG. 24 is an illustration of an embodiment of an unexpandedsegmented stent placed in the circumflex branch of the heart;

[0035]FIG. 25 is an illustration of an embodiment of a segmented stentplaced in the circumflex branch of the heart with a first group ofsegments expanded;

[0036]FIG. 26 is an illustration of an embodiment of the stentillustrated in FIG. 25 after shrink segments have been radiallyexpanded;

[0037] FIGS. 27A-27D are illustrations of various embodiments of ashrink segment; and

[0038] FIGS. 28A-28C are illustrations of various embodiments of a hooksconnected to a traction segment.

DETAILED DESCRIPTION

[0039] In the following description, for purposes of explanation and notlimitation, specific details are set forth in order to provide anunderstanding of the disclosed subject matter. However, it will beapparent to one skilled in the art that the disclosed subject matter maybe practiced in other embodiments that depart from these specificdetails. In some instances, detailed descriptions of well-known methodsand devices are omitted so as not to obscure the description of thedisclosed subject matter with unnecessary detail.

[0040] In an embodiment, the apparatus and method relate to stent 100,which is illustrated in FIG. 1. In an embodiment, stent 100 includes acylindrical body made up of a number of radial traction segments 110(e.g., radial traction segments 111, 112 and 113), and one or moreshrink segments 140 (e.g., shrink segments 141 and 142). Each radialtraction segment contains a pattern of struts 115. In an embodiment,struts 115 may connect directly to one another, or may be connected bylinks 117. Struts 115 may be configured in a number of strut patterns,such as multi-link, duet, pentagonal, or others. FIG. 1 shows anembodiment with zig-zag patterned struts 115 and link 117. Stent 100 maybe made of a material suitable for residence within a blood vessel.Suitable materials include, but are not limited to, a shaped-memoryalloy, nickel titanium, stainless steel alloys, cobalt chrome alloys,nickel alloys and platinum alloys. Stent 100 may include one or moretherapeutic or medicinal coatings to improve its compatibility with ablood vessel. Individual segments of stent 100 may also includevisualization markers coated thereon or embedded therein (e.g.,radiographic, magnetic resonance, etc.).

[0041] In one embodiment, stent 100 placed near a mitral valve regionmay be used to deliver or release a drug or therapeutic agent to treatmitral valve regurgitation. Various drugs are known in the art fortreating mitral valve regurgitation. For example, administeringnitroprusside (a vascular smooth muscle relaxant) may effectivelydiminish the amount of mitral regurgitation, thereby increasing forwardoutput by the left ventricle and reducing pulmonary congestion.Inotropic agents such as dobutamine may also be administered to increasethe force of contraction of the myocardium. In one embodiment, the stent100 may be coated with these exemplary drugs for delivery near themitral valve region. The drugs may have timed-release features to bereleased slowly over a certain period of time. The drug eluting supportannulus or other devices may also have the drug or agent dispersed onthe surface of the support annulus or other devices, or co-dissolved ina matrix solution to be dispersed on the support annulus. Methods tocoat the support annulus with a therapeutic drug include dip coating,spin coating, spray coating, or other coating methods commonly practicedin the art.

[0042] In some cases, patients with defective heart valves may haveconcomitant coronary artery disease (CAD). As such, it may beadvantageous for stent 100 to deliver a drug to treat occlusions in theartery or other related CAD such as vulnerable plaque. The drug to treatCAD may be delivered alone or in combination with drugs to treat mitralvalve regurgitation. Drugs to treat CAD include, but are not limited to,statins, lipid lowering agents, antioxidants, extracellular matrixsynthesis promoters, inhibitors of plaque inflammation and extracellulardegradation, estradiol drug classes and its derivatives.

[0043] In one embodiment, the drugs to treat CAD may be coated on astent 100 using methods such as dip coating, spin coating, spray coatingor other coating methods known in the art. The drug may alternatively beencapsulated in microparticles or nanoparticles and dispersed in acoating on the support annulus or other device. A diffusion limitingtop-coat may optionally be applied to the above coatings. The activeagents may optionally be loaded on a support annulus or other devicetogether either by adding them together to the solution of the matrixpolymer before coating, or by coating different layers, each containinga different agent or combination of agents. The drug eluting the stentmay alternatively have an active agent or a combination of agentsdispersed in a bioerodable annulus forming polymer.

[0044] Stent 100 is of dimensions suitable to be inserted into a bodylumen, such as the coronary arteries or coronary veins. In oneimplementation, the stent 100 is of dimensions suitable to be insertedinto a right coronary artery or the circumflex branch. After insertion,each radial traction segment 110 may be expanded by a balloon or otherknown method. Upon expansion, struts 115 may make radial contact withthe inner surfaces of the body lumen so as to maintain stent 100 in afixed position in the body lumen.

[0045] In an embodiment, stent 100 may also include hooks 105, which maybe coupled to radial traction segments 110. The hooks 105 may beembodied in various shapes and forms. FIGS. 28A-28C represent varioushook members 105 that may be used with the stent 100. In the illustratedembodiments, the hook members 105 include one or more sharp sections 106provided at one end thereof. The sharp sections 106 formed on the hookmembers permit the stent to firmly attach to an interior wall of a bodyvessel, as the radial traction segments are radially expanded. As shownin FIG. 28A, the hook member 105 may also include an arm section 107extending between traction segment 110 and the sharp sections 106.

[0046] In an embodiment, hooks 105 are only connected to radial tractionsegments 110 located at either horizontal ends of stent 100 (e.g.,radial traction segment 111 and 113, respectively, in the embodimentshown in FIG. 1). In other embodiments, hooks 105 may also be coupled toradial traction segments 110 that lie in the interior of stent 100. Uponexpansion of radial traction segments 110, hooks 105 will be seated inan inner surface(s) of the body lumen to provide further radialtraction. It is appreciated that hooks 105 may also be coupled tosegments 140 in other embodiments, or may be attached to any structuresplaced at either horizontal end of stent 100 or any structures placedbetween radial traction segments 110 and/or 140.

[0047] As stated above, in an embodiment, stent 100 also includes one ormore shrink segments 140 (e.g., linear shrink segments). Shrink segments140 may include struts 145. Struts 145 are biased at angles so that asshrink segment 140 is expanded, shrink segment 140 decreases inlongitudinal length. When one or more shrink segments decrease inlength, the overall length of stent 100 decreases, thus constituting aninner surface of the body lumen in which stent 100 is seated.

[0048] Various patterns may be used to construct a shrink segment. FIGS.27A-27D represent a number of patterns that may be used in shrinksegments 140. The shrinks segments shown in FIGS. 27A-27D include anumber of radially expandable cells. In one embodiment, each radiallyexpandable cell is configured such that, as the cell is expanded in aradial direction, its axial length will decrease. FIG. 27A is anillustration of an embodiment of the shrink segment 140, in which eachradially expandable cell 172 has a square configuration with strutsdisposed in slanted orientation with respect to a longitudinal axis ofthe shrink segment. FIG. 27B is an illustration of an embodiment of theshrink segment 140, in which each radially expandable cell 174 has adiamond configuration. FIG. 27C is an illustration of an embodiment ofthe shrink segment 140 having an alternating slots pattern 176. It is tobe appreciated that the slot pattern 176 formed in the shrink segmentshown in FIG. 27C will deform as the shrink segment is radiallyexpanded, causing its longitudinal length to decrease. FIG. 27D is anillustration of an embodiment of the shrink segment 140 having analternating axial/radial slots pattern 178.

[0049]FIG. 2 is a close up illustration of an embodiment of unexpandedshrink segment 142. FIG. 3 is a close up illustration of shrink segment142 following expansion (designated expanded shrink segment 142′).Shrink segment 142 may be expanded in a radial direction by variousmeans, including with a balloon. In an unexpanded state, shrink segment142 has a longitudinal length of SL₁ and a radial height SH₁. Followingexpansion from SH₁ to SH₂ (FIG. 3), shrink segment 142′ has alongitudinal length SL₂, which is less than SL₁. Accordingly, when hooks105 have been seated, and shrink segments 140, including shrink segment141 and shrink segment 142, are expanded, the length of shrink segments140 will each decrease from SL₁ to SL₂. The reduction in the length ofsegments 140 will cause radial traction segments 110 to be pulled towardone another, thereby reducing an overall length of stent 100. Referringagain to FIG. 2 and FIG. 3, when the radial height of shrink segment 142is increased by Δ_(SH) (i.e., SH₂ to SH₁), the longitudinal length ofshrink segment 142 is decreased by Δ_(SL) (i.e., SL₁ to SL₂). Inembodiments, the ratio of Δ_(SL):Δ_(SH) may be varied by modifying thepattern of struts 115. As described below, struts 115 may be designedsuch that the Δ_(SL):Δ_(SH) ratio is 2:1, 1:1, 1:2 or other ratios.

[0050] Referring again to FIG. 1, in an unexpanded state, stent 100 hasa total length defined as TSL₁. Stent 100 can be manufactured with alength that is suitable for insertion into a coronary sinus orcircumflex branch of the left coronary artery. The coronary sinus andcircumflex branch are positioned, in a typical heart, exterior to theleft atrium and left ventricle approximate portions of the mitral valveannulus. Stent 100 can be placed in one or both of the coronary sinusand circumflex branch to inhibit the mitral valve annulus fromlengthening (e.g., getting larger in diameter). By constricting aportion of the coronary sinus and/or circumflex branch in this area, anatrioventricular valve annulus (e.g., mitral valve annulus) can also beconstricted to an appropriate degree. Representatively, in terms of themitral valve, by constricting the mitral valve annulus, cusps orleaflets can be brought closer together to improve aptation (coaptation)and reduce regurgitation. Additionally, the height and length of thevarious segments 110 and 140 may vary so as to construct stent 100 in ashape that is tapered to conform with the particular blood vessel orbody lumen into which it is inserted.

[0051] Stent 100 may include various combinations of radial tractionsegments 110 (segment 111, segment 112, and segment 113) and shrinksegments 140 (segment 141 and segment 142). For example, in theembodiment illustrated in FIG. 1, stent 100 includes alternating radialtraction segments 110 with one shrink segment 140 disposed between eachof radial traction segments 110. In other embodiments, stent 100 couldinclude a number of radial traction segments 110 placed adjacent to oneanother, or a number of shrink segments 140 placed adjacent to oneanother. It is also appreciated that stent 100 may include variousquantities of shrink segments 140. The embodiment of stent 100illustrated in FIG. 1 includes three radial traction segments 110 andtwo shrink segments 140. However, in other embodiments, stent 100 mayinclude only one shrink segment 140, or more than two shrink segments140. Stent 100 may include any number of radial traction segments 110.Additionally, the quantity of radial traction segments 110 may be evenor odd, and the quantity of shrink segments 140 may also be even or odd.

[0052]FIG. 4 is an illustration of an embodiment of segmented balloon200. In an embodiment, balloon 200 includes a number of segments thatcorrespond to segments of stent 100 (FIG. 1). Representatively, in FIG.2, balloon segments 211, 212 and 213 correspond to radial traction stentsegments 111, 112 and 113 of stent 100. Balloon segment 241 correspondsto shrink stent segment 141 and balloon segment 242 corresponds toshrink stent segment 142 of stent 100. Balloon segments 211, 212, 213,241 and 242 may be inflated individually, in groups, or all at once.Additionally, balloon segments 211, 212, 213, 241 and 242 may be eitherpartially inflated to varying degrees or may be completely inflated. Ifballoon segments 211, 212, 213, 241 and 242 are fully inflated, thecorresponding stent segments will be expanded to a first degree. In anembodiment, if balloon segments 211, 212, 213, 241 and 242 are partiallyinflated, they will exert a force on the corresponding stent segmentsthat will cause the corresponding stent segments to expand to a degreethat is less than the first degree.

[0053]FIG. 5 is an illustration of an embodiment of segmented balloon200 in which only a group of balloon segments corresponding to radialtraction segments 110 have been inflated. A suitable balloon material issimilar to dilation catheter balloons or stent placing balloons.Balloons 200 may be inflated according to conventional techniques, forexample, suitable liquid delivered at a proximal end of a catheter.Segments 211, 212 and 213, which correspond to radial traction segments110 of stent 100, may be expanded individually, all at once, or ingroups. Upon expansion, balloon segments 211, 212 and 213 will exertforce on the respective corresponding stent segments (i.e., stentsegments 111, 112 and 113), therefore causing these stent segments toexpand. The embodiment of segmented balloon 200 illustrated in FIG. 5includes five inflatable segments corresponding to radial tractionsegments and shrink segments of the stent 100. However, in otherembodiments, segmented balloon may include any number of inflatablesegments (e.g., 1, 2, 3, 4, etc). For example, the same inflatablesegment of the balloon may be used to expand more than one segment ofthe stent by deflating the inflated segment, realigning the inflatablesegment to align with another segment of the stent and reinflating theballoon segment.

[0054] In one embodiment, the segmented balloon 200 includes a number oflumens with separate lumens for inflating separate balloon segments(e.g., by delivering liquid to separate segments of the balloon). Forexample, as seen by referring to FIG. 5A, a cross-sectional view of thesegmented balloon taken along line A-A′ of FIG. 5 shows multiple-lumens.In the embodiment illustrated in FIG. 5A, there are three lumens250-252. One lumen 250 is provided in the segmented balloon to inflatedall segments 211, 212 and 213, which correspond to radial tractionsegments 110 of stent 100. The other lumens 251 and 252 are provided toinflate individual segments 241 and 242, which correspond to shrinksegments 140 of stent 100. By providing individual lumens 251 and 252for the segments 241 and 242, one segment of the segmented balloon 200may be inflated independent of other segments of the balloon 200. FIG.5B shows cross-sectional view of a distal end of the segmented balloontaken along line B-B′ of FIG. 5. As shown in FIG. 5B, only one lumen 250corresponding to the last remaining segment 213 is provided at thedistal end of the segmented balloon. In the illustrated embodiment,three lumens 250-252 are shown; however any number of lumens may beprovided in a segmented balloon to allow one or more segments to beinflated independent of other inflatable segments.

[0055]FIG. 6 is an illustration of an embodiment of stent 100 afterballoon 200 has been inflated in the manner illustrated in FIG. 5. Asshown in FIG. 6, upon inflation of balloon 200 in this manner, segments111, 112 and 113 of stent 100 will be expanded, but segments 141 and 142of stent 100 will not be significantly expanded. In an embodiment, theexpansion of stent segments 110 will seat hooks 105 into an innersurface of a body lumen such as the interior wall of the coronary sinussurrounding the mitral valve annulus to provide radial traction betweenstent 100 and an inner surface of a body lumen.

[0056]FIG. 7 is an illustration of an embodiment of segmented balloon200 having balloon segments 241 and 242, which correspond to linearshrink segments 141 and 142, respectively, inflated, in addition tosegments 211, 212 and 213 (See FIG. 3). As balloon segments 241 and 242are inflated, force is applied to linear shrink segments 141 and 142,thus causing expansion of segments 141 and 142. FIG. 8 is anillustration of an embodiment of stent 100 after expansion of linearshrink segments 141 and 142. As discussed above, the longitudinal lengthof linear shrink segments 140 reduces from a length SL₁ (prior toexpansion) to a length of SL₂ upon expansion. As such, upon expansion,the total length of stent 100 is reduced by a length of R×(SL₁−SL₂),where R is the total number of segments 140 that are expanded. The totallength of stent 100 following expansion of segments 140 is defined asTSL₂.

[0057] In one embodiment, the linear shrink segments 141 and 142 areradially expanded one at a time. For example, after one segment of theballoon has been inflated to radially expand one of the linear shrinksegments 141 and 142, the inflated segment of the balloon may bedeflated prior to adjustment of a different shrink segment. It should benoted that once the catheter balloon has been used to reduce a length ofone of the linear shrink segments, realignment of the balloon withrespect to the stent (e.g., by using visualization markers such asradiopaque markers) may be necessary prior to adjustment of differentshrink segment.

[0058] In another embodiment, two or more linear shrink segments (e.g.,segments 141 and 142) may be radially expanded at the same time. In thisembodiment, the segmented balloon may be configured so that, as eachlinear shrink segment reduces in its longitudinal length, the individualinflatable segments of the balloon will maintain proper alignment withthe individual segments of the stent.

[0059] Referring to FIGS. 1 and 27A-27D, a shrink segment may includes anumber of radially expandable cells, in which each cell is configuredsuch that, as the cell is expanded in a radial direction, its axiallength will decrease. In embodiments shown in FIGS. 1, 27A and 27B, eachradially expandable cell is formed with a number of slated strutsconfigured such that, as each cell is expanded in a radial direction, abias angle between the slated struts and a longitudinal axis increasesto cause its axial length to decrease. It is to be appreciated that, theangles between struts 145 in linear shrink segments 140 may be biased atdifferent angle so as to control the degree of reduction in length ofeach linear shrink segment 140 upon expansion.

[0060] Representatively, FIG. 1 illustrates an embodiment in which thestruts of each unit cell 151 are biased at 45° angles (angled α). Aseach unit cell 151 is expanded in the radial direction, the bias anglebetween the diagonally disposed elements and the longitudinal axis willincrease, causing the longitudinal length (L) of each unit cell 151 todecrease. Upon expansion, at a 45° strut bias, the longitudinal lengthshrinkage: vertical height expansion ratio for each unit cell 151 is1:1. Specifically, upon expansion, the reduction in longitudinal length(L) of the individual unit cell 151 is substantially equal to theincrease in vertical height (H) of the cell 151. It should be understoodthat the amount of linear shrinkage of a shrink segment is function ofthe number of unit cells around the circumference of the shrink segmentand the number of unit cells in the longitudinal direction.

[0061] In one embodiment, a shrink segment is capable of shrinkinggreater than 10% in the longitudinal direction. In another embodiment, ashrink segment is capable of shrinking greater than 25% in thelongitudinal direction. For example, in one implementation, for a shrinksegment having struts biased at 45° angles, a longitudinal length of 6.8mm and a diameter of 2 mm, an increase in the diameter of 0.5 mm willcause a 2.66 mm reduction in the longitudinal length.

[0062] In another embodiment, illustrated by FIG. 9, struts 145 arebiased at a 30° angle (angled α). Upon expansion, at a 30° strut bias,the longitudinal length shrinkage: vertical height expansion ratio foreach unit cell 152 is 2:1. As such, upon expansion, the reduction inlongitudinal length (L) of the individual cell 152 may be approximatelytwice the increase in vertical height (H) of the cell 152. Accordingly,when a 30° strut bias is employed, the total length of stent 100 will bereduced to length TSL₃ that is shorter than the total length TSL₂ ofstent 100 when it is shrunk with struts 140 at a 45° strut bias. Thebias angle is measured relative to a longitudinal axis of the stent. Itis appreciated that struts 145 may be biased at various different anglesas one means of regulating the degree of longitudinal shrinkage of stent100.

[0063] As discussed above, in regard to radial traction segments 110,various strut designs are adequate and can be used to practice thedisclosed subject matter. In one embodiment, the traction segments 110are configured to maintain its axial length substantially constant asthe traction segments 110 are expanded in a radial direction. FIGS.11-14 represent a number of strut designs that may be used in radialtraction segments 110. FIG. 11 is an illustration of an embodiment ofradial traction segment having struts 115 in a zig-zag pattern. In anembodiment, a radial traction segment 100 also includes link 117. One ormore struts may be connected by link 117. FIG. 12 is an illustration ofan embodiment of radial traction segment 110 having struts in a zig-zagpattern, and having an additional cross strut. The cross struts tend toadd to the tensile strength of the segment. FIG. 13 is an illustrationof an embodiment of radial traction segment 110 having a loop pattern ofstruts. FIG. 14 is an illustration of an embodiment of a stent segmenthaving a loop pattern with an additional cross strut. The cross strutstend to add to the tensile strength of the segment.

[0064] In an embodiment, stent 100 and balloon 200 may be configured toexpand each linear segment 140 of stent 100 individually, in groups, orall at once. One way this may be accomplished is through a multi-lumenballoon 200 (e.g., with separate lumens corresponding to separateballoon segments). As stated above, in an embodiment, segments 211, 212and 213 corresponding to radial traction segments 110 (e.g., radialtraction segments 111, 112 and 113, respectively) are typically firstinflated to seat hooks 105. After hooks 105 have been seated, in anembodiment, linear shrink segments 141 and 142 may be expanded one at atime by expanding individual balloons corresponding to each particularsegment. In this regard, FIG. 15 is an illustration of an embodiment ofballoon 200 in which, among the balloon segments corresponding to linearshrink segments, only segment 242 corresponding to a shrink segment 142is inflated (inflation illustrated by reference numeral 242′). Segment241 is not inflated and, as such, shrink segment 141 that corresponds toballoon segment 241 will not expand. FIG. 16 is an illustration of stent100 following inflation of balloon 200 as illustrated in FIG. 15. Uponexpansion of stent segment 142, the total length of stent 100 will bereduced from length TSL₁ to length TSL₄. In an embodiment, length TSL₄will be greater than length TSL₂, which as described above, was obtainedwhen all shrink segments 140 were expanded at the same time, asillustrated in FIG. 8. As such, by inflating balloon segments 240 one ata time, or in a group that does not include all balloon segments 240,the degree of reduction in length of stent 100 will be reduced.Additionally, in an embodiment, by inflating balloon segments 210 one ata time, or in groups, stent 100 may be gradually reduced to size TSL₁,which is a length of stent 100 after all linear shrink segments 140 havebeen expanded. Balloon segments 240 may be expanded over varying periodsof time, as required by the person administering stent 100. For example,one linear shrink segment 140 could be expanded to introduce a firstdegree of reduction in the length of stent 100. Then, a few months later(or whatever time frame is determined to be appropriate), anotherballoon segment 240 may be inflated to expand a different linear shrink140, thereby further reducing the total length of stent 100.

[0065] In an embodiment, balloon segments 240 may be partially inflatedso as to partially expand stent segments 140. FIGS. 17-18 areembodiments of balloon segment 242 partially inflated to a height H₁(illustrated by reference numeral 242′). By partially expanding stentsegments 140, the degree of reduction in the length of linear shrinksegments 140 will be less than the degree of reduction in length that isobtained when shrink segments 140 are completely expanded. In thisregard, FIG. 19 illustrates stent 100 following inflation of balloon 200in the manner illustrated in FIGS. 17-18. Shrink segment 142 ispartially expanded to reduce the length of shrink segment 142 to lengthSL_(I). SL_(I) is greater than SL₂, which is the length of shrinksegment 142 upon full expansion. As a result of this reduction in thelength of linear shrink stent segment 142, the total length of stent 110is reduced to TSL₅, which is greater than the length of stent 110 iflinear shrink stent segment 142 is fully expanded.

[0066] As shown in FIGS. 20-21, in an embodiment, balloon segments 240may be further inflated so as to further expand partially expandedshrink segments 140. For example, balloon segment 242, which, as shownin FIGS. 17-18, may be expanded to intermediate height H₁, may befurther expanded to H₂. Upon this further expansion of segment 242, thecorresponding linear shrink segment will be further expanded and shrinklongitudinally as shown in FIG. 22 (illustrated by reference numeral242″). In this manner, the length of stent 110 may be gradually reduced.In such embodiments, balloon segments 140 may be partially inflated, andthen further inflated any number of times so as to gradually reduce thelength of a shrink segment 140, and to gradually reduce the overalllength of stent 110. In an embodiment, balloon segments 240 may befurther inflated until full expansion, thereby fully expandingcorresponding stent segments 110.

[0067]FIG. 23 is a diagram showing a top cross-section of human heart300 taken through the right and left atrium. Human heart 300 includesmitral valve 320 and tricuspid valve 360. Mitral valve 320 issubstantially surrounded by mitral annulus 325. A portion of circumflexbranch 330 runs close (externally adjacent) to a portion of mitral valve320, exterior to the left atrium and left ventricle. A portion ofcoronary sinus also extends close (externally adjacent) to a portion ofmitral valve 320.

[0068]FIG. 24 is an illustration of an embodiment of unexpanded stent100 disposed in a body lumen near a valve annulus (e.g., circumflexbranch 330, coronary sinus, coronary artery). Unexpanded stent 100 maybe delivered to the body vessel by various delivery methods. Forexample, the stent may be delivered to a desired location within thepatient's body by mounting the stent on an expandable member, such as aballoon catheter, provided on a distal end of an intravascular catheterand a sheath extending, for example, from a proximal end of the catheterover the stent. A guide catheter may be routed through a femoral arteryinto the aorta and into, for example, the circumflex branch of the leftmain coronary artery, possibly with the aid of a guide wire. Theintravascular catheter including the stent may then be advanced throughthe guide catheter and positioned at a desired location with, forexample, a suitable visualization technique. The exterior sheath may beretracted to expose the stent. FIG. 24 shows stent 100 mounted onintravascular catheter 350 and positioned within circumflex branch 330.

[0069] To place a stent (such as stent 100) in the coronary sinus from afemoral artery, a guide catheter and possibly a guide wire may first beintroduced through the inferior vena cava and into the right atrium. Oneexemplary guide catheter for delivering a stent to a desired locationwithin, for example, a coronary sinus, is described in acommonly-assigned U.S. patent application Ser. No. XX/XXX,XXX, AttorneyDocket No. 005618.P3546, filed Nov. 12, 2002 to Eric T. Johnson andCindy Sherman, entitled “Guide Catheter,” which is hereby incorporatedby reference.

[0070] According to one aspect, the stent inserted into a body lumennear a mitral valve annulus or tricuspid valve annulus serves to supportand/or constrict a surface of a valve annulus of an antrioventricularvalve. In one embodiment, the stent may be inserted in the coronarysinus or the circumflex artery or both to inhibit an annulus surroundingthe mitral valve from lengthening. In another embodiment, certainsegments of the inserted stent are capable of shrinking in length asthey are radially expanded so that the stent can be used to constrict asurface of a body lumen near an antrioventricular valve annulus so as toreshape the valve annulus. When an antrioventricular valve such as amitral or tricuspid valve fails to close completely, the segmented stentmay be used to constrict a surface of a body lumen near the valveannulus so as to cause the heart valve to close properly and to reducethe severity of regurgitation during ventricular contraction.

[0071]FIG. 25 is an illustration of an embodiment of stent 100 afterportions of the segmented stent are securely attached to an interiorwall of circumflex branch 330. In one embodiment, this is accomplishedby inflating certain segments of a catheter balloon once the stent hasbeen inserted into a desired location so as to expand radial tractionsegments against the interior wall (see, e.g., FIGS. 5-6 and theaccompanying text). Alternatively, the segments are secured one at atime with a balloon catheter having a single balloon (e.g., bypositioning the balloon within a radial segment, inflating, deploying,then repositioning). When the radial traction segments are expandedagainst the interior wall, hooks 105 on the radial traction segmentswill become securely seated to the body lumen surface. As describedabove, when segments 140 are unexpanded, stent 100 has a length TSL₁. Asecond length LM₁ is defined as a length of a segment of surface 322 ofmitral valve 320 that is generally parallel to the portion of innersurface 332 of circumflex branch 330 which defines TSL₁. FIG. 25 showscatheter 35 retracted proximal to stent 100.

[0072] Once the stent has been securely implanted, certain segments ofthe catheter balloon may be inflated so as to radially expand one ormore of the shrink segments (see, e.g., FIGS. 7-22 and the accompanyingtext). By doing so, the shrink segments, which shrink in length as theyare radially expanded, will pull radial traction segments toward oneanother. Certain ones of the radial traction segments that are connectedto the inner wall of the circumflex branch 330 (for example, throughseated hooks 105) will tend to cause a length of circumflex branch 330to constrict. The stent 100 illustrated in FIG. 25 after shrink segments140 have been radially expanded is shown in FIG. 26. Upon expansion ofshrink segments 140, the length of shrink segments 140 collectivelydecrease the length of stent 100 from TSL1 to TSL2. Seated hooks 105constrict inner surface 332 of circumflex branch 330, as tractionsegments 110 are pulled together by shrink segments 140. Theconstriction of inner surface 322 of circumflex branch 320 causesvertical force, F_(V), and horizontal force, F_(H), to be applied tosurface 322 of mitral valve 330. Forces F_(V) and F_(H) result inreinforcement of, and/or indirect constriction of surface 322 of mitralvalve annulus 325. According to one aspect, the constriction of thesurface of an atrioventricular valve annulus reshapes the valve annulusso that the valve (e.g., mitral valve) closes properly and reducesregurgitation. As such, regurgitation may be reduced withoutannuloplasty.

[0073] In one embodiment, each shrink segment of the segmented stent isconfigured to be reduced in length over a range of longitudinal length,as it is radially expanded. This allows the overall stent length to beselectively adjusted over a defined ranged of longitudinal length.Accordingly, an operator (e.g., physician) may readjust the longitudinallength of the stent, after the initial insertion, if additionalconstricting of an annulus surrounding a heart valve is required. Forexample, a balloon catheter (e.g., a multi-lumen balloon catheter) maybe reinserted into a patient and positioned within stent 100.Visualization techniques may be used to properly position the balloon.Representatively, visualization markers (e.g., radiopaque markers) maybe present on stent 100 or the balloon segments of a balloon catheter orboth. Once positioned, selected shrink segments may be modified toconstrict/expand a blood vessel (e.g., circumflex branch 330) to reshapean antrioventricular valve annulus.

[0074] FIGS. 24 to 26 illustrate a stent structure (stent 100) placed ina circumflex branch of the left coronary artery. It is appreciated thata similar structure may alternatively or additionally placed in thecoronary sinus adjacent a portion of the mitral valve annulus. It isalso appreciated that the stent or method described may be used in avariety of body lumens or vessels, not just those adjacentatrioventricular valve annulus, to support or constrict the body lumenor structures adjacent the body lumen.

[0075] While the foregoing embodiments have been described and shown, itis understood that variations and modifications, such as those suggestedand others within the spirit and scope of the following claims, mayoccur to those skilled in the art to which the invention pertains.

What is claimed is:
 1. An apparatus comprising: a tubular member ofdimensions suitable for insertion into a body vessel, the tubular memberhaving at least two first segments attachable to an interior wall of thebody vessel, and at least one second segment disposed between the firstsegments, wherein said at least one second segment is capable ofdecreasing its axial length to draw one of the first segments towardsthe other first segment, wherein the tubular member is capable ofreducing a longitudinal length of a portion of the body vessel bydrawing one of the first segments attached to a first portion of thebody vessel towards the other first segment attached to a second portionof the body vessel.
 2. The apparatus of claim 1, wherein the tubularmember serves to inhibit a portion of the body vessel from lengthening.3. The apparatus of claim 1, wherein the second segment decreases itsaxial length as the second segment is expanded in a radial direction. 4.The apparatus of claim 1, wherein each of the first segments isconfigured to maintain its axial length substantially constant as thecorresponding first segment is expanded in a radial direction.
 5. Theapparatus of claim 1, wherein the second segment is configured such thatan amount of reduction in the axial length of the second segment isgreater than an amount of increase in the diameter of the secondsegment.
 6. The apparatus of claim 1, wherein the first segmentscomprises a plurality of radially expandable cells, each of saidradially expandable cells configured such that, as the respective cellis expanded in a radial direction, its axial length remainssubstantially constant.
 7. The apparatus of claim 1, wherein the secondsegment comprises a plurality of radially expandable cells, each of saidradially expandable cells configured such that, as the respective cellis expanded in a radial direction, its axial length decreases.
 8. Theapparatus of claim 1, wherein the second segment comprises a pluralityof radially expandable cells, each of said radially expandable cellscomprises a plurality of slanted struts configured such that, as eachcell is expanded in a radial direction, a bias angle between the slantedstruts and a longitudinal axis increases to cause a longitudinal lengthof each cell to decrease.
 9. The apparatus of claim 3, wherein thelongitudinal length of the second segment is selectively adjustable overa range of longitudinal length by controlling the amount of expansion inthe radial direction.
 10. The apparatus of claim 1, wherein the secondsegment is capable of shrinking greater than 10% in the longitudinaldirection.
 11. The apparatus of claim 1, wherein the second segment iscapable of shrinking greater than 25% in the longitudinal direction. 12.The apparatus of claim 1, wherein the second segment is capable ofshrinking greater than 2 mm in the longitudinal direction.
 13. Theapparatus of claim 1, wherein the second segment is configured toprovide radial support so as to prevent the tubular member from bucklinginward.
 14. The apparatus of claim 1, wherein said first segmentsincludes a plurality of hooks capable of attaching to the interior wallof the body vessel as the corresponding first segment is expanded in aradial direction.
 15. The apparatus of claim 1, wherein each segment ofthe tubular member is expandable independent of other segments.
 16. Theapparatus of claim 1, wherein the tubular member is coated with a drugto treat valve regurgitation.
 17. The apparatus of claim 1, wherein thetubular member is provided with a medicinal coating to increasecompatibility with a blood vessel.
 18. The apparatus of claim 1, whereinthe tubular member is of dimensions suitable to be inserted into atleast one of coronary arteries and coronary veins.
 19. The apparatus ofclaim 18, wherein the tubular member is of dimensions suitable to beinserted into to one of a coronary sinus, a right coronary artery andcircumflex coronary arteries.
 20. The apparatus of claim 1, wherein thetubular member is a stent.
 21. The apparatus of claim 1, wherein thetubular member is self-expanding.
 22. The apparatus of claim 1, whereinthe tubular member comprises one of a shaped-memory alloy, nickeltitanium, stainless steel alloys, cobalt chrome alloys, nickel alloysand platinum alloys.
 23. The apparatus of claim 1, wherein the tubularmember is provided with visualization markers.
 24. A catheter ballooncomprising: a plurality of inflatable segments, wherein a set ofinflatable segments is capable of being inflated independent of otherset of inflatable segments.
 25. The catheter balloon of claim 24,further comprising a plurality of lumens, each lumen configured toinflate one or more inflatable segments.
 26. The catheter balloon ofclaim 24, further comprising at least one segment capable of beingpartially inflated to varying degrees, wherein when the segment ispartially inflated, the segment exerts a force on a corresponding stentsegment to cause the corresponding stent segment to partially expand.27. A method comprising: inserting a tubular member into a body vessel,said tubular member having at least two attachable portions; andattaching the attachable portions of the tubular member to an interiorwall of the body vessel.
 28. The method of claim 27, wherein the tubularmember attached to the body vessel prevents a portion of the body vesselfrom increasing in length.
 29. The method of claim 27, furthercomprising drawing one of the attachable portions towards the otherattachable portions to reduce the length of a portion of the bodyvessel.
 30. The method of claim 27, further comprising coating thetubular member with a drug to treat valve regurgitation.
 31. The methodof claim 27, wherein the tubular member is placed in a coronary sinus.32. The method of claim 27, wherein the tubular member is placed in acircumflex artery.
 33. The method of claim 27, wherein the tubularmember is placed in a right coronary artery.
 34. The method of claim 27,further comprising tightening an annulus surrounding a mitral heartvalve by reducing a longitudinal length of the attached tubular member.35. The method of claim 27, further comprising tightening an annulussurrounding a tricuspid heart valve by reducing a longitudinal length ofthe attached tubular member.
 36. The method of claim 27, wherein thetubular member comprises at least two traction segments having aplurality of hooks, said traction segments expandable to seat theplurality of hooks in the body vessel.
 37. The method of claim 36,wherein the tubular member further comprises at least one shrink segmentcoupled between the traction segments, said at least one shrink segmentcapable of decreasing in longitudinal length to draw one of the tractionsegments towards the other traction segment.
 38. The method of claim 36,wherein the drawing one of the traction segment towards the othertraction segment comprises expanding the shrink segment in a radialdirection.
 39. The method of claim 27, wherein the tubular membercomprises a plurality of expandable segments.
 40. The method of claim39, further comprising selectively expanding at least one segment of thetubular member without expanding other segments of the tubular member.41. The method of claim 40, further comprising adjusting a longitudinallength of the tubular member by selectively expanding the shrink segmentin a radial direction